commit c82807df1d1650cad617d9149d34bd2fc97e89d6
parent 43d2dc4e27d4eb0131b9a31df60b5830c3cfa89b
Author: Johannes Lorenz <[email protected]>
Date: Sat, 15 Jun 2013 17:38:06 +0200
Started phaser docs, still experimental.
Diffstat:
2 files changed, 27 insertions(+), 0 deletions(-)
diff --git a/doc/effects.txt b/doc/effects.txt
@@ -499,3 +499,30 @@ Its parameters are being used by the comb and allpass filters.
* *Pan* lets you apply panning. This is the last thing to happen. Set it to 0.0
to only hear output on the right side.
+
+Phaser
+~~~~~~
+
+The Phaser is a special dynamic filter. The result is a sweeping sound, which is
+often used on instruments with a large frequency band, like guitars or strings.
+This makes it typical for genres like rock or funk, where it is often modulated
+with a pedal, or for giving strings a warm, relaxing character. In ZynAddSubFX,
+the phaser can currently only be modulated with an LFO.
+
+The audio signal is split into two paths. One path remains unchanged. The other
+one is sent to a delay line. The delay time (the so called *phase*) is made
+dependent on the frequency. Therefore, an all-pass filter is applied to the
+signal, which *preserves* the amplitude, but determins the delay time. In the
+end, both paths are added.
+
+The following picture describes how this works on white noise. Light blue
+signalises that the frequency is not present at the current time, and dark blue
+signalises the opposite. The dark blue peaks appear if the delay time is very
+short, because then, the second path almost equals the first one, which results
+in duplication of the signal. If the delay line is very long, then it is --- in
+the case of white noise --- totally at random whether the delayed signal
+currently duplicates the unchanged path, or whether it cancels it out to zero.
+This random effect results in white noise between the clear blue structures.
+
+image::./images/phaser-spectrogram.jpg[width="700", title="Spectrogram of an
+8-stage phaser modulated by a sine LFO applied to white noise."]
diff --git a/doc/phaser-spectrogram.jpg b/doc/phaser-spectrogram.jpg
Binary files differ.
